Several years ago, the present inventor devised an optical to tactile converter device to allow blind people to "read". This device converted printed or other optical text or material directly into a corresponding tactile image by means of an input silicon photo-camera, which sensed the input image and produced a corresponding pattern of output signals which operated an electromechanical tactile stimulator. In the original device, the tactile stimulator was comprised of ceramic bimorphs, which vibrate pins in a two-dimensional array to produce the output tactile image.
As an improvement over the above device, the present inventor devised a tactile stimulator of improved design comprising a stack of sheets of piezoelectric polymer material, which, in the preferred embodiment, is polyvinylidenefluoride (PVF.sub.2), with each sheet having two opposed broad flat faces and at least one tactile surface at one longitudinal end. It was determined that upon the application of a voltage of a predetermined magnitude and polarity from an external source applied across the electrodes sandwiching said sheet material, the sheets longitudinally extend their tactile surfaces. By proper employment of the above-described physical structure, selective areas of the tactile surface of the stack of planar sheets could be extended, thus providing a tactual reading source for the blind.
It has now been described that similar technology could be used as a means of sensing force or motion by using the same sheet material in conjunction with an electrode pattern to generate an electric signal in response to a force or motion. It was determined that such a device, when placed, for example, at the "fingertips" of a robotic arm, would provide a sensitivity much greater than that previously realized by the prior art. In fact, it was determined that not only could one "sense" that the device had contacted a foreign object but even the shape and size of the sensed object could be determined.